1. Field
The present disclosure relates to computer-generated animation and, more specifically, to rendering a computer-generated animation using a dependency graph.
2. Related Art
A computer-generated animation is typically created by rendering a sequence of images, with each image depicting a computer-generated scene composed of one or more computer-generated objects (e.g., a character, tree, table, chair, etc.). Light sources, materials, textures, and other visual effects may be associated with the computer-generated objects to create realistic lighting effects for the computer-generated scene. Properly implementing these visual effects can involve configuring large amounts of data used by numerous external processes, such as rendering, shading, rasterizing, shadowing calculations, reflection calculations, transmission calculations, and the like. Managing the configuration data and external processes can be difficult due to the large amount of data and large number of processes required to produce a computer-generated animation and the complex dependencies that exist between them.
For example, film production lighting typically requires a lighter to configure tens to thousands of outputs to be used by external processes for each shot in a computer-generated animation. These outputs may depend from multiple inputs, which may in turn depend from other inputs and/or external processes. For example, the lighter may be required to select one or more light sources (e.g., ambient light source, point light source, spotlight, or the like) used to illuminate the computer-generated scene as well as configure surface shaders to simulate the optical properties (e.g., color, texture, specular properties, and the like) of each surface of each computer-generated object in that scene. Thus, the appearance of an object in the scene depends on, among other things, the one or more light sources and the outputs of the external shading processes used to simulate the optical properties of the various surfaces of that object.
As more light sources and objects are added to the scene, the dependencies between the configuration data and the external processes become exceedingly complex. Moreover, complex assignments of lighting configurations may be used such that some lighting configurations are assigned on an object-by-object basis, while others are assigned to groups of objects identified by a shared attribute. For example, a spotlight may be associated with only the main character in the foreground of the scene, causing the spotlight to illuminate the main character and not the other objects in the scene. The scene may also include an ambient light associated with all objects in the scene. This approach provides the animator or lighter with more flexibility when configuring the visual effects in a scene, but may result in increased complexity for the lighter since traditional lighting work-flows require the lighter to commit the intricate data dependencies between the external processes to memory. Additionally, traditional lighting work-flows require the lighter to explicitly modify the lighting configurations as objects in a scene are edited, added, or removed, creating a substantial amount of work for the lighter.
It is therefore desirable to create a system for configuring and managing the configuration data and external processes used to render a computer-generated animation.